Frequency regulation of systems distributing power and time



June 19, 1934. H. E. WARREN 1,963,727

FREQUENCY REGULATION OF SYSTEMS DISTRIBUTING POWER AND TIME OriginalFiled Jan. 8, 1929 5 Sheets-glen l \kg /0/-- Z! Ww I I 4 Inventor: :04:04 Henry ElWarren,

by H IS Attorney.

June 19, 1934. WARREN 1,963,727

FREQUENCY REGULATION OF SYSTEMS DISTRIBUTING POWER AND TIME OriginalFiled JaLn. 8, 1929 v5 SheetsSheet 2 Fig. 2. I Fig.3.

68 88 my 7. 07 r Inventor: Henry E. Warren His Attorney.

June 19, 1934. H E, WARREN 1,963,727

FREQUENCY REGULATION OF SYSTEMS DISTRIBUTING POWER AND TIME OriginalFiled Jan. 8, 1929 5 Sheets-Sheet 3 Inventor: Henry EWarre n,

His Attorney June 19, 1934. H. E. WARREN FREQUENCY REGULATION OF SYSTEMSDISTRIBUTING POWER AND TIME Original Filed Jan.-8, 1929 5 Sheets-Sheet 4lid Inventor: Henry 'E. Warren by HIS Attorney.

June 19, 1934. E. WARREN 1,963,727

FREQUENCY REGULATION OF SYSTEMS DISTRIBUTING POWER AND TIME OriginalFiled Jan. 8, 1929 s Sheet s-Sheet 5 Fig. I8.

CIRCUIT FROM MASTER CONTROLLR .35

CIRCUIT FROM MASTER GLOGK CONTACTS 55'34' Inventor Henry E. Warren,

His Attorney.

Patented June 19, 1934 UNITED STATES PATENT OFFICE FREQUENCY LREGULATION OF SYSTEMS DISTRIBUTING POWER AND TIME Henry E. Warren,Ashland, Mass., assignor to Warren Telechron Company, Ashland, Mass., a

corporation of Maine t Original application January 8, 1929, SeriallQo.331.149. Divided and this application April 16,

1931, Serial No. 530,708

4 Claims. (Cl. 171 119) .10 filed April 24, 1930, contains claimsdirected to certain aspects of the matter disclosed herein relating topower control apparatus.

The control of the frequency of alternating current distribution systemsby means of master l5 clocks to permit of the distribution of time bymeans of synchronous motor driven secondary clocks is now well known.Such a system is described in my Patent 1,420,896. In such systems themaster clock serves to measure the integrated error in frequency of thesystem and to control the speed of the power generating apparatus so asto correct for the error by raising or lowering the instantaneousfrequency until the integrated error has been corrected.

Owing to the extensive interconnection of power, systems it becomesincreasingly important from the power plant operating standpoint thatthe instantaneous frequency -as well as the integrated frequency shallbe closely regulated since appreciable changes in instantaneousfrequency generally result in a disturbing influence on the loaddistribution between different generating units and generating plantsconnected to the system. By means of the present invention theintegrated frequency and the instantaneous frequency are both maintainedat high accuracy. In carrying my invention into effect I provideapparatus for measuring the integrated frequency error over small timeintervals, for example over two second intervals. The error thusmeasured may be less than l/400th of a second and because of theshortness of the time interval, and the inertia of power generatingapparatus it is likewise an approximately correct measure- 45.ment ofthe error in instantaneous frequency.

'Automatic apparatusis provided for regulating one or more of the primemovers of the power generating apparatus in a manner to correct for anyerror thus determined and the extent of Q such regulation isproportional'to the 'error as measured during each interval. Thus Iobtain a a practically continuous automatic regulation which iscorrective of extremely small errors in the frequency of the system.

Furthermore, I preferably select the total allowable integrated errorwithin which it is desired to maintain the frequency and proportion thisallowable selected integrated frequency error to the total amount ofregulation available and thenmaintain a similar relation between the 00actual total integrated frequency errorand the degree of regulation. Forexample let us assume it is desired to keep within a total integratedfrequency error of five seconds and the available amount of regulationcorresponds to the regulation of a 5,000 kw. power unit from no load tofull load. If then the measured integrated frequency error of the systemis three seconds slow the regulation of the power unitis maintained suchthat it delivers 3,000 kw. If the integrated frequency error increasesto. four seconds the power unit will begadjusted to deliver 4,000 kw.

If the regulation of one such power unit isinsuflicient to maintain thefrequency within the allowable error additional power units in the sameor in different stations are brought under control such for example thatthe available regulation corresponds to the regulation of 10,000 or50,000 kw. of energy or whatever amount is suflicient to maintain theintegrated frequency error of the system within the, allowable limit.

Where a number of power generating units are regulated in accordancewith my invention, I also include automatic means for maintaining theproper load distribution between the various units being regulated.Other objects and novel features of my invention will appear from thedescription which follows:

The features of my invention which are believed to be novel andpatentable will be pointed out in the claims appended hereto. For abetter understanding of the invention reference is made in the followingdescription to the accompanying drawings which represent in Fig. 1 ageneral as sembly drawing of the desirable parts of "my improvedregulating apparatus as applied to the regulation of a multiple unitwater power generating station for large distribution systems; Fig. 2 isa front view of the frequency error measuring device which I have chosento call an automatic master clock; Fig. 2a shows a portion of the masterclock in a different operative position than that in Fig. 2; Fig. 3 is aside view of the master clock represented in Fig. 2; Figs. 4 and 5 areside and end views respectively of the master controller which is adevice which receives corrective current impulses from the master clock,transforms theminto proportional rotative motions in a commutator deviceand distributes these movements electrically to various controlling andindicating devices, certain aspects of which are claimed in my copendingapplication Serial No. 402,508, filed October 25, 1929; Fig. 6 is asectional view of one of the several motion reproducing motors operatedfrom the master controller; Figs.

- device with a portion of the front cover broken away; Fig. 14 a planview with the top cover removed, and Fig. 15 a side view as seen fromthe left side of Fig. 13 with that side of the casing removed, togetherwith a motion transmitting motor which is operated in accordance withthe extent of gate opening of the water turbine or the load on thegenerator driven by such turbine or other source of power. Fig. 140. is'a view of a contact device as removed from the case of the unitcontroller in order to more clearly illustrate its construction; Fig. 16shows how the control may be made dependent on the power output of thepower generating unit instead of dependent on the gate opening of theprime mover and also how the master clock pendulum may be biased inresponse to certain load conditions; Fig. 17 represents a switchingarrangement for changing from automatic to manual control and viceversa; and Figs. 18, 19 and 20 represent simplified embodiments of myinvention.

In Fig. 1 I have represented a hydroelectric power generating stationcontaining water turbines 20 driving alternating current generators 21.The number of such generating units which may be controlled by a singlemaster clock controller may vary. Also the capacity of the differentunits controlled'may be different and the prime movers may be steamturbines or prime movers of other types. Each prime mover is equippedwith the usual speed governing apparatus represented at 22 and theapplication of my improved regulating system thereto involves no specialmodification of such existing governing mechanism. The electric motorrepresented at 23 may be the usual motor employed to alter the governoradjustment so as to increase or decrease the speed of the unit from thestation switchboard in the synchronizing operation. Many other devicesfor varying the speed of the source of power or for correcting the speedof the generator or other alternating current apparatus may be adaptedto this method of automatic speed regulation; such for example as thosedescribed in my United States Patents 1,420,896, 1505,925 and 1,522,216.24 represent the supply pipes for the water turbines, 25 the leversoperated from the governors which regulate the gate opening and 26represent electric motion transmitters geared to the turbine gateoperating mechanism whereby the extent of gate opening may betransmitted to the unit controllers. The generators 21 are connected tosupply the outgoing feeder bus 27, and 28 is a transformer for supplyingthe low voltage circuits of my improved frequency regulating apparatusfrom The control apparatus of my invention is arranged to maintain theinstantaneous frequency and the average frequency of the system suppliedby the power station at a high degree of accuracy by regulating the gateopenings of the dulum 31 and a synchronous motor 32 energized fromsystem 2'7 through transformer 28 and con- I ductors 101 and 102. Acomparison is made between the rate of the pendulum and the motor everytwo seconds. If the frequency is exactly correct, the relation of thesynchronous motor to the pendulum will be constant, but if the frequencyis high or low the synchronous motor will run slightly fast or slowduring these two second intervals. The error, if any, which accumulatesduring this small time interval is measured even though the amount maybe less than 1/400th of a second in time. As soon as an error isdetected by the master clock it opens one or the other of the sets ofcontacts 33 or 34 depending on whether the error is positive or negativeand the duration of opening is proportional to the error. These contactsactuate the master controller represented generally by the referencecharacter 35. The master controller is operated by two motors 98 and 99best shown in Fig. 4. One motor is controlled by contacts 33 and servesto drive the commutator device 38 in one direction and the other motoris controlled by contacts 34 and serves to drive the commutator device38 in the opposite direction. The extent of travel of the commutatordevice 38 duringa two second interval is dependent upon the duration ofopening of the contact at 33 or 34. The master controller 35 is thuscaused to send out electrical current impulses which are transmittedover the circuits 39 to a number of receiver motors 40, 41, 42 and 43,all of similar constructiomwhich reproduce the motion of the commutatingdevice 38. The motor 40 is arranged to correct the relation between thependulum 31 and synchronous motor 32 at the end of each time interval byan amount corresponding to the error measured so as to place the masterclock controller in a condition to accurately measure the error in thenext succeeding time interval. The motor 41 operates a station indicator44 which shows at all times the accumulated error, if any, in thefrequency. The rotor of motor 41 is geared down to two hands 45 and 46such for example that one hand makes a complete revolution for onesecond accumulated error in frequency and the other makes a completerevolution for twelve seconds accumulated error in frequency. When noerror exists the two hands correspond to the position of 12 oclock on aclock dial and move 'to the right or left to indicate positive ornegative errors in integrated frequency.

It will be evident that owing to the small time interval employed andthe magnified motion of the fast moving hand of the indicator this handlikewise serves to indicate very clearly the instantaneous errors infrequency because if this hand continues at rest the observer may besure that the instantaneous frequency is correct even though there maybe an accumulated integrated frequency error.

Motors 42 and 43 serve to reproduce the movement corresponding to thefrequency error as integrated over the two second interval at the unitcontrollers indicated by reference characters 47 and 48. These unitcontrollers are similar and are employed to regulate the two-primemovers to correct for thefre quency errors and to maintain a desiredload distribution between the power units. a

tegrated frequency error. The integrated frequency error is transmittedto the unit controller through the motors 42 and 43 while the extent ofgate opening as measured by the motion transmitting devices 26 istransmitted to the unit controllers through the motion reproducingmotors 49 and 50. These two quantities are indicatedon a dial bypointers 52 and 51. Thetwo movements are compared by means of adifferential and .the speed adjusting motors 23 are controlled from thedifferential through special contact devices 53 to maintain the gateopening proportional to the allowable integrated frequency error and tokeep the instantaneous frequency error approximately zero.

I prefer to'combine with the master clock controller 30 signal deviceswhich will call attention to abnormal frequency errors. Such signaldevices may comprise lamps 55v and 60 and an alarm 61, which devices arecontrolled by adjustable back contacts' 62 and 63. Ordinarily thesecontacts are not closed by the master clock regulator, but in case thefrequency error as measured over a two second interval increases to anabnormal extent these contacts are intermittently closed, therebyinforming the station attendant that abnormal load changes are takingplace and the direction thereof, suchforiexample as may necessitate thestarting up of another power generating unit. These auxiliary contacts62 and 63 may also serve to disconnect the automatic control mechanismwhen'abnormal conditions occur. For this purpose a time delay relay 200is connected in circuit with the alarm 61 and is arranged to open aswitch 201 through which suitable parts of the control apparatus areenergized. The opening action of switch 201 by relay 200 is delayed by adash-pot 202 so that unless the abnormal conditions continue for severalseconds the switch will not be opened.

Having thus briefly outlined the general character and function of thecombined apparatus 1 will now proceed to describe the details andoperation of the several novel devices starting with the master clock,the details of which are best shown in Figs. 2 and 3. 4

The starting point of the control system is a high accuracyfree pendulum31. The pendulum should be mounted on a solid foundation free fromvibration and should be compensated for changes in temperature. It ispreferably provided with suitable means for adjusting its rate such as asmall platform 64 upon which graduated weights 65 may be placed. Forpurposes of automatic rate adjustment of the pendulum, an example ofwhich willhereinafter be explained, I may also provide it with a smallpermanent magnet 66 near its free end and place a stationary magnetizingcoil 67 adjacent to the path of movement of the pendulum. Now if thecoil is energized with direct current so as to produce a repelling forceon the permanent magnet it will have the same effect as a decrease ofgravity causing the pendulum to decrease its rate. If the current incoil 67 is reversed its. vfield "will attract the magnet 66 and producethe opposite effect and an increase in the rate of the pendulum. Thismaster clock preferably operates a clock, a portion of the dial of whichis represented at 203. The clock mechanism is not shown since it is oldand its operation is well known. The secondary clock system comprisessynchronous motor driven clocks represented at 204 and such secondaryclocks may be connected to any part of the distribution system fed bythe generating apparatus the frequency of which is controlled by themaster clock 30. As will presently appear the error between the masterclock 30 and the secondary clocks connected to the system will underordinary conditions not exceed a few seconds and will never besufficient to create a noticeable time error in the secondary clocks. I

Pivoted at 68 nea r,the point of suspension of the pendulum 31 is asmall weight lever 69 having an extended flexible rod 70 for the purposeof periodically impressing the pressure of the lever against thependulum rod 31. The weight lever 69 rests against the surface of a cam'71 which is so shaped that for a small portion of its revolution theflexible rod 70 will be free to press against the pendulum rod 31 but atall other positions in the revolution of the cam there will be nocontact between the pendulum rod and the rod 70. The cam '71 is driventhrough suitable gearing from the synchronous motor 32 so arranged thatone complete rotation of the cam normally corresponds to the doublevibration of the pendulum and the relation of the parts is such thatduring the left hand swing of the pendulum the rod 70 will rest againstthe pendulum rod for a short distance both sides of the center of theswing of the pendulum. This force keeps the pendulum 31 in oscillation.

It is a fact that impulses imparted to a swinging pendulum at the centerof its stroke cause a minimum disturbance of its rate of oscillation.This condition of course requires approximately correct phase relationbetween the revolving cam 71 and the swinging pendulum and such phaserelation must be established and can only be maintained by propercorrespondence between relation of the cam and the pendulum and forcorrecting errors in this phase relation are provided in the followingmanner:

Loosely pivoted at 72 is a short pendulum 73 having an upward flexibleextension 74. The pivot bearing 72 preferably is mounted upon anadjustable eccentric 75 of which the angular position is shown by apointer 76 and scale 77 to enable the position of pivot 72 to beadjusted with exactness. The slot 78 in the pendulum 73 is such that thependulum may be freely lifted past the pivot 72, but if free to drop,the upper end of the slot will rest against the pivot 72. Thelower endof the pendulum 73 at point 79 is interfered with by the lever 69, whenthe latter is in the position shown in the drawings. If however lever 69were sufficiently depressed, pendulum 73 would swing to the left and thedistance to which it would swing to the left would be determined byinterference between the lower end of the pendulum at point 79 and thesloping upper surface of the lever 69.

When the phase relation of the cam 71 which revolves clockwise and themain swinging pendulum 31 is correct, the lever 69 which has beencontact occurs the lever 69 drops downward at a rate corresponding tothe velocity of the pendulum rod 31. Soon after rod 70 has beenpermitted to rest against pendulum rod 31 and has thereby impartedpressure corresponding to'the weight of the lever 69 in a directiontending to accelerate the pendulum 31, the auxiliary free pendulum '73will be released at the point '19 and this pendulum will swing quiterapidly, on account of gravity, toward the left,,keeping pace with theleftward swing of pendulum 31 and the correspondingly increasing angulardepression of lever 69. Meanwhile, the cam '71 continuing in itsrevolution, will soon reach a position where it will again pick up thelever 69 together with the free pendulum '73 which is now resting uponthe upper surface of this lever and will forcibly raise the two partsupward. Consequently the pressure of '10 against pendulum rod 31 will bereleased and pendulum 31 will continue its left hand swing until itreaches the end of its travel, when it will return toward the rightwithout any contact whatever on its right hand swing with the rod '70,for the reason that the rod has been moved far enough to the right bythe cam 71 to entirely clear pendulum rod 31 as it swings to the right.

The final position of the free pendulum '73 with respect to the lever 69will depend entirely upon the angle to which the lever 69 has dropped atthe instant when it is pushed up by the revolving cam '71. Consequentlythis position will depend upon the phase relation between the cam '71and the pendulum rod 31; Fig. 2a shows one relation of these parts justprior to the upward movement of lever 69 by cam 71.

Any gain in speed of the cam above normal would cause the lever 69 to bepushed upward with a smaller angle of slope and consequently a lessdisplacement toward the left of the pendulum '73 while speed belownormal of the cam '71 will tend to bring about the later lifting of thelever 69 with a consequently greater angle of slope and a greaterdisplacement toward the left of the pendulum '73.

As a result of these activities the upper end at the point 81 will moveupward when the lever 69 is lifted by the cam in different positionsalong a horizontal line, which positions will depend entirely upon thephase relation between the cam '71 and the pendulum 31. If the phaserelation of these two members is correct the point 81 will enter thespace at 82 between the two flexible contactors 83 and 84 so as not toaffect either of these contactors when the pendulum '73 is pushed upwardby the action of the cam '71. If, however, the cam '71 is fast withrespect to the pendulum rod 31, point 81 will be at the left hand of thegap 82 and when the free pendulum '73 is. pushed upward contact 83 willbe lifted open circuit it at adjustable contact point 33. The cam '71has a gradually reduced radius from the point 85 in a counterclockwisedirection to the point 86 and as a result the free pendulum '73 will begradually lowered after it has reached its extreme height and as aresult the duration of the circuit opening at point 33 or 34 as the casemay be will be measured by the amount of the which will q left hand orright hand deviation of the point 81 from its midposition 82 when thefree pendulum is lifted. This is on account of the step formation at theends of the contactors 83 and 84; consequently, if the error in thephase relation between the cam '71 and the pendulum 31 is very slight sothat push rod '74 comes up only a little to the right or left of point82 there will be a brief opening of circuit at points 33 or 34 but ifthe deviation is considerable there will be a correspondingly greaterduration of opening at points 33 or 34.

As the cam '71 continues its revolution after having lifted lever 69with free pendulum '73 on top and consequently displaced either one orthe other of contactors 83 or 84 and has again been lowered there willcome a time when a pin 8'7- projecting from the back face of the camwill'engage a slender downward extension 88 of the pendulum '73 so as toforce this free pendulum to the right along the upper surface of thelever 69 and beyond the right hand end of this lever intothe positionshown in Fig. 2 where the pendulum 73 rests lightly against the outerend of thelever 69. The mechanism is then ready for the next cycle ofoperations.

Of the several position indicating motors in the circuits 39 controlledby the master controller 35 the one 40 mounted on the master clock isfor the purpose of correcting the phase relation between the cam '71 andthe moving pendulum 31.

This motor, through reduction gears 89, 90, 91 and 92 is attached bymeans of ratio gears 93 and 94 directly to the casing 95 of thesynchronous motor 32 which drives the cam '71. The arrangement beingsuch that this entire motor casing with the reduction gearing which itcontains, as in my-Patent 1,495,936, can be rotated freely within thepoles of the field 32. The circuit connections are such that therotation of the position indicating motor 40, as a result of the phaseerror between the revolving cam '71 and the pendulum.31 with theresultant opening of one of the contacts 33 or 34, will immediatelyshift the cam '71 which is directly driven by the motor 32 through thegears 96 and 9'7, either forward or backward by an angle correspondingapproximately with the amount of the error in phase, so that if nofurther phase shifting should occur, the upper end of the free pendulum73 on its next upward movement passes through the space 82 between thecontactors 83 and 84. If any residual error remains there will be afurther similar correction at the next upward stroke of the pendulum'73. If the error in the frequency of the system continues thesynchronous motor 32 will again shift cam 71 out of its correct phaserelation with the pendulum 31 and then the correction action willberepeated at every complete oscillation of the pendulum so long as thefrequency is in error. This means that the cam '71 will be maintainedvery close .to its correct phase relation to the pendulum 31 by periodiccorrections substantially equal to the amount of the error accumulatedduring each oscillation of the pendulum and the corrections will ofcourse be greater or less according as the error in frequency is greateror less.

The gear reduction ratio of the motor 32 is designed for the standardfrequency to be regulated so that when the frequency is normal the cam'71 will make one revolution in two seconds, or the time required for adouble vibration of the pendulum 31. 'I'he'pendulum 31 having beenaccurately adjusted to a. rate of one complete frequency whichaccumulate in each two secondinterval and actuate the contact devices 33or 34 in accordance with the direction and extent of such errors. Theapparatus is sufllciently sensitive to detect and correct for an errorof 1/500th of a second in a two-second interval. Any error sufllcientlygreat to actuate the corrective control contacts will also set intooperation the motor 40 to substantially correct the phase relationbetween the cam 71 and pendulum 31 at the end of the interval. As aresult of this correction of the phase relation after each operation ofthe contact there is no tendency for the apparatus to overshoot and huntin the control of the prime movers as would otherwise be the case.

The next piece of apparatus to be described is the master controller 35shown in detail in Figs. 4 and 5 and which is controlled by the masterclock through normally closed contacts 33 and 34. The master controlleris driven by a reversible electric motor device comprising two motors 98and 99. Each of these motors may be selfstartingsynchronous motors, likethe motor 32.

The rotors of these motors are mounted on the same shaft containedwithin the upper extension of the gear casing 100 (see Fig. 4). Themotors are arranged to drive the shaft in opposite directions. As shownin Fig. 1, both motors are normally energized motor 98 being connectedfrom supply line 101 through normally closed contact 33 through themotor field to the other supply line 102. Motor 99 is connected fromsupply line,

101 ihrough normally closed contact 34, the motor field coil, back toline 102. In this constantly energized condition of the two field coilsthe shaft on which the rotors are mounted remains stationary but theinstant contact 33 is opened by the master clock, motor 99 drives theshaft in one direction. Likewise, the opening of contact 34 permitsmotor 98 to drive the shaft in the opposite direction. In this manner Iam able to minimize coasting of the motor device when it isv desired tostop it and at the same time to retain the benefit of the extremelyrapid acceleration which is characteristic of this type of selfstartingsynchronous motor. The action in response to certain changes produced bythe master clock at points 33 and 34 is exceedingly prompt and dead beatand the extent of movement produced is proportional to the duration ofthe opening of the contact at 33 or 34 as the case may be.

This motor device drives, through suitable reduction gearing, a portionof which is indicated at 103, a pair of commutator brushes 104 and 105preferably of the roller type which make contact with a stationarycommutator having '12 equally spaced segments 106. The roller contacts104 and 105 are carried by arms extending from a shaft 103A indicated indotted lines in Fig. 4. Gear 103 is mounted on this shaft and the shaftis supported ,in a framework having end pieces 107 and 108 mountedbetween bolts 109 extending through an insulating base support 110. Thisbase supports the commutator segments and the driving motors and isprovided with suitable electric terminals for making the necessaryconnections. A carbon brush 111 is pressed against the end of shaft 103Aand serves to convey current to the metallic rollers 104 and 105.

The circuit connections for the commutator distributor are shown inFig. 1. It will be noted that the 12 stationary contacts are arranged ina threephase, four-wire arrangement with Y connections. Every thirdsegment is connected together corresponding to a three-phase circuitrepeated four'times. The three parallel connected sets of contacts areconnected to the three distribution lines 39 which extend to the variousposition reproducing motors 40, 41, 42 and 43.

The movable brushes 104 and 105 are connected .to one side of the sourceof supply by line 101; The three field coils of the position reproducingmotors are connected on one side to the lines 39 and on the other sideto a Y- point connected to the other side of the source of supplythrough line 102. This type of motion transmitting system may beenergized by either direct or alternating current.

The preferred construction of the motion. reproducing motors and theoperation of this motion reproducing system will now be described inconnection with Figs. 6 to 12 inclusive. A very desirable constructionfor the motion reproducing motors such as are represented at 40, 41, 42and 43 is shown in Fig. 6 and consists of three-separate fields 115, 116and 117 the exciting coils of which are connected as shown in Fig. 1, aspreviously explained. Each field is provided with two bar rotors allmounted on the same shaft. If the line of magnetization produced by thethree field coils lies in the same plane the six bar rotors will bedispersed equally over 360 degrees, as represented in Figs. 6 and 7,where the rotors are lettered a, b, c, d, e and f respectively, a and bbeing the rotors in field 115,0 and d the rotors in field 116, and e andf the rotors in field 117.

In Fig. 7 the position of the commutator brushes 104 and 105, which aredisplaced from each other by a suitable angle for the purpose ofproperly spacing the impulses in the three phases of circuit 39, aresuch as to energize field only. Consequently, its two rotors a and bwillbe equally influenced and take the position represented in this figure.

In Fig. 8 the brushes have been rotated counter.'

receiver with the coils and rotors which are active indicated in eachcase.

Thus it will be seen that with this arrangement there are six differentangular positions of the rotor of the otion receiving motor for eachcomplete cyclic ghange of the current which causes a half. revolution ofthe motor. Two revolutions of the motor, or 24 different positions,correspond to one revolution of the transmitting commutator. Theapparatus operates in the same manner in either direction. All of theposition indicating motors 40, 41, 42 and 43 being connected to the samecircuit 39 and the source of supply in multiple will of course movesimultaneously and to the same extent. I consider that this motiontransmitting system has certain novel features and to be particularlyadvantageous in the control system disclosed, but I of course do notlimit my invention to any particular motion transmitting system.

Attention is next directed to the unit controllers shown at 47 and 48 inFig. 1. One of these unit controllers is shown in detail in Figs. 13, 14and 15 and since they are similar the detail description of one willsuffice.

Before proceeding with the detail description it will seem desirable tostate that the main purpose of this unit controller is to compare theintegrated frequency error, as summed up by the motion reproducing motor42, with the gate opening of the prime mover 20 as transmitted to theunit controller by the motion reproducing system comprising transmitter26, transmitting lines 120 and receiver 49 and to automatically controlthe speed adjusting motor 23 of the prime mover governing mechanism soas to maintain a gate opening which is proportional to the integratedfrequency error. By means of the device 26 we obtain an approximatemeasurement of the relative power output of the power unit as comparedto its maximum power output capacity. This measurement is compared tothe total integrated frequency measurement of the system by thedifferential mechanism of the unit controller and the unit controllerautomatically controls the power output of the generating unit throughits speed adjusting means so as to maintain a power output approximatelyproportional to the total integrated frequency error of the system. Letus assume for example that, with the auto matically controlled primemovers 20 adjusted so as to deliver no power but with other powergenerating apparatus, not shown, delivering the minimum powerrequirements of the system and maintaining the frequency such that theintegrated frequency error of the system is uro, additional load istaken from the system such as to produce a slight lowering of the systemfrequency. Immediately the master clock regulator detects this loweringof the frequency and transmits the integrated errors as measured overtwosecond intervals to the unit controllers. These unit controllers openthe gates of the controlled prime movers by an amount proportional tosuch error. The additional load supplied by the automatically controlledunits does not wipe out the accumulated integrated frequency error butmerely brings the instantaneous frequency back to normal so that nofurther error accumulates unless the load changes. Additional load mayresult in a further accumulated frequency error causing a furtheropening of the turbine gates of the automatically controlled units.Likewise, a decrease in load may produce a slight increase in frequencyand a lowering in the accumulated frequency error. This causes the unitcontrollers to close the turbine gates by a proportional amount so as toimmediately bring the instantaneous frequency back to normal. The totalallowable integrated frequency error corresponding to full gate openingmay be, and preferably is, made very small; for example, one-third of asecond. A suflicient number of automatically controlled generating unitsare of course provided to control the frequency of the entire system inthis way such that the integrated frequency error never exceedsone-third of a second. Thus the automatic control maintains theinstantaneous frequency error at approximately zero and maintains theintegrated frequency error at such a low value that it has nosignificance upon the use of the system for the correct distribution oftime by secondary clocks. An exceptionally uniform load control of theentire system is obtained without'hunting, such that extensivedistribution systems may be controlled without disturbing influencestending to shift load from one power plant to another and the principalreason for this is that the automatic controller of my invention is farmore sensitive and precise than the usual speed governor. The unitcontroller represented in Figs. 13, 14 and 15 is an important element inthe control scheme just outlined and will now be explained.

The motion reproducing motor 42 which is responsive to the integratedfrequency error changes drives a shaft 121. This shaft is geared to ashaft 122 carry g a long pinion 123. The two sets of gears representedbetween shafts 121 and 122 are for the purpose of changing the gearratio if that becomes desirable to make the device responsive to a totalallowable. integrated frequency error of one second, for example, and tocorrespondingly decrease the rate of regula tion. A gear 124 integralwith a nut 125 and a sleeve 126 is driven from the pinion 123. Sleeve126 drives a pointer 51 through a sliding connection comprising collar128 and pins129. This pointer 51 indicates the integrated frequencyerror on a dial 130.

The motor 49 connected to the gate opening transmitter 26 through lines120, drives a worm shaft 133 through gears 131 and 132. The shaft 133extends forward and carries a pointer 52 in front of the dial 130. Thispointer thus indicates the gate opening on the dial 130. As a result therelation between the. integrated frequency error and the gate openingmay be visually compared on .the dial. Zero integrated frequency errorand zero gate openingpreferably correspond to approximately a twelveoclock position of the pointers on the dial. Pointer 52 makessubstantially a complete revolution in a clockwise direction for acomplete opening of the turbine gate and pointer 51 makes substantiallya complete revolution in a clockwise direction for the total permittedintegrated frequency error caused by a lowering of the frequency belownormal. Adjustable stop pins 124a are preferably provided on .theperiphery of wheel 124 to limit the rotation of this wheel as desired soas to limit the automatic control to any desired range of gate opening.A complete revolution of pointer 51 may correspond to one-third of asecond integrated frequency error. The shaped or colored so as todistinguish them.

The relation between the gate opening and integrated frequency error isalso compared mechanically by this device through a differentialmechanism which so controls the circuit of speed control motor 23 as tomaintain the two hands 51 and 52 in the same or approximately the sameposition on the dial, or so as to ma ntain the gate opening proportionalto the allowable integrated frequency error. Shaft 133 carries a wormthread 134 which the internally threaded nut 125 meshes. Thus a turningof shaft 133 corresponding to a gate opening movementmoves nut 125towards the dial or downward, as viewed in Fig. 14. A turning of nut 125correspond'ng to an increase in the integrated frequency error moves nut125 away from the dial. Simultaneous turning of both shaft 133 and nut125 in the same direction and at the same rate produces no longitudinalmovement of the nut at all. Longitudinal movement of nut 125 is employedto move the flexible contact arm 135 up and down as viewed in Fig. 14.This contwo hands are differently ner of mounting this contact drive isrepresented in Fig. 14a which shows the arm, together with its mounting,removed from the case in a position corresponding to that in Fig. 13.The shaft 137 supports an arm 138 which carries at its free end a roller139. Roller 139 is held against the rear end of nut 125, see Figs. '14and '15, by a spring 140. Consequently this roller, together with arm138 will follow the movement of nut 125. This movement is transferred tocontact arm 135 through an upward extending pin 141 on arm 138 adownward extending pin 142 on the insulating block 136 and a spring 143exerting pressure tending to keep the two stop pins in contact.Normally, arm 138, contact arm 135 and nut 125, move back and forthtogether. Springs 140 and 143 however permit an abnormal movement ofcontact arm 135 in either direction without bringing undue pressure onroller 139 such as might cause breakage or displacement of the parts incase automatic operation of any port'on of the apparatus should besuspended as hereinafter explained.

The free end of contact arm 135 is forked and cooperates with a pair ofcontacts 144 and 145.

This contact device is designated generally by the reference character53 in Fig. 1. Contacts 144 and 145 are'insulated from each other andmounted on a shaft 146 which is driven by a motor 147 at one revolutionin a. few seconds. The two contacts 144 and 145 are helical in shape andso driven that the portions of the contacts opposite to the contact arm135 approach the latter. This not only provides a wiping contact and arapid break but what is more important, it provides a duration ofclosure which is proportional to the displacement of contact arm 135from its central position. The internally threaded insulating sleevesupon which the two helical contacts are mounted may be turned on thethreaded shaft 146 for the purpose of adjusting the spacing betweenthem. A hub of conducting material is provided with each helical contactagainst which brushes 148 rub to provide the necessary circuitconnections. The circuit connection to contact arm 135 is represented at149.

The arrangement and adjustment of .the parts are such that when thehands 51 and 52 are together at any position on the dial 130 corresponding to a gate opening which is proportional to the integrated frequencyerror, contact arm 135 is equi-distant from contacts 144 and 145 and nocontact with either is made for any rotative position of shaft 146 andconsequently no current impulses are sent to the speed control motor 23(Fig. 1). If now motor 42 is actuated in response to an error infrequency as detected by the master clock, for example by an error whichincreases the total integrated frequency error, nut 125 will be turned,moving pointer 51 in a clockwise direction and roller 139 and contackarm 135 up as viewed in Fig. 14, thereby bring ng the forked end ofcontact arm 135 in opening is immediately transferred to motor 49 whichturns shaft 133 and pointer 52 in a clockwise direction by anamount-which again approximately alines the two hands and moves nut 125,roller 139 and contact lever 135 back to a central position. This actionis repeated every time the master clock detects a frequency error andthe magnitude and direction of regulation is such as to correct the insantaneous frequency permitting the total integrated frequency error tovary with the gate openng within the limits determined by the adjustmentand calibration of the apparatus.

The action of the master controller is preferably modifled by astabilizing mechanism which permits a limited amount of resilientendwise movement of the shaft 133 during the operation of the apparatus.It will be noted that the endwise position of shaft 133 is normallybiased to its. proper position by the collar 150, Fig. 14. This collaris held between two arms 151 and 152 which are pivoted on the frameworkat 153 and 154 respectively. A spring 155, the central portion of whichis broken awayin Fig. 14, normally holds arms 15,1 and 152 againstadjustable stops 156 and 157 to correctly locate the endwise position ofshaft 133. This arrangement thus permits" a resilient endwise movementof shaft 133 in either direction if sufficient force is exerted butreturns the shaft to its correct position as the force is removed. Thisresilient device for determining the endwise position of shaft 133 actsagainst a dash-pot 158 (see Fig. 15). The dash-pot 158 is connected toshaft 133 through a coarse pitch worm 159 on the shaft, an internallythreaded nut 160 and a lever 161. The lever is pivoted at 162. One endis forked and embraces pins .on nut 160 which prevents the nut fromturning and the other end is pivoted tothe plunger of the dash-pot. Withthis arrangement, whenever shaft .133 is turned, nut 160 tends to bedisplaced endwise. Rapid'displacement of nut 160 in an endwise directionis resisted by the dash-pot and as a result whenever shaft 133 is turneda considerable amount in the operation of the device in response to amovement of the turbine gate there may occur both an endwisedisplacement of the nut 160 in one direction and a displacement of shaft133 in the opposite direction. The action of the dash-pot andconsequently the amount of endwisedsplacement of shaft 133 under suchconditions may be adjusted by a valve in the dashpot piston as indicatedat 162, Fig. 15.

The pitch of worm 159 is opposite to that of Worm 134 embraced by nut125 so that the action of the dash-pot is to momentarily check the fullcontrolling action of the master controller on the speed control motor23. This steadying ziction may be explained as follows: So long as thetwo hands 51 and 52 are together, the position of'the nut 125 and theshaft 133 will be such that no contact is made at 144 or 145, andtherefore no current impulses are sent to the speed control motor 23.When an error in the integrated frequency occurs so as to rotate nutposition tobe wiped by contact 144. Owing toa 125 an axial motion of nut125 will occur and the helical shape of contact 144 the duration of suchcontact will depend upon the amount of displacement of arm 135 which isof course dependent on the magnitude of the error integrated by themaster clock in the two second interval. .Speed control motor 23 is,thus energized for a corresponding interval causing a proportionateopening of the turbine gate. The change in gate contact will be madebetween contact arm 135 and one of the helical contacts 144 or 145, thussending corrective impulses to the speed control motor 23. As soon asthe turbine gate moves, the shaft 133 will begin to revolve and thiswill tend to restore the correct relationship between the two hands 51and 52. This will also tend to bring the contact arm 135 back to itsneutral position through the action of worm 134 on nut 125. This actionwill be assisted by motion of the screw thread 159 on nut 160 which willmove the shaft endwise in opposition to one of the spring pressed levers151 or 152 because during this action the resistance of the dash-pot 158will prevent material axial motion of the nut 160. Consequently thecorrecting action upon the speed control motor will be checked beforethe two hands 51 and 52 are together, but after checking of thecorrective action occurs, the dash-pot piston will very slowly yield tothe pressure placed upon it by the spring 155 acting through the screwthread 159 and nut 160 so that a further very gradual additionalcorrection of the speed controller will be permitted by a furthercontact of very short duration at 144 or 145 as the case may be.Consequently, the hands 51 and 52 will slowly continue to approach theiralined relationship and the device will not be in final equilibriumuntilthese two hands are together. It will be observed that after acorrection in one direction the device is ready at alltimes for a veryprompt correction in the opposite direction so that if overcorrectionshould occur on the first impulse, the

.slow motion of the dash-pot under the influence of the spring 155 willactually be added to the effect due to divergence of the hands. Theresult of the dash-pot and its associated parts is thus to preventover-correction and racing of the controlling function while permittingexoeedingly' correct regulation of the frequency with a minimum amountof turbine gate adjustment in a minimum interval of time.

The anti-racing effect of the dash-pot is not always needed, and thisfeature may then be omitted.

The motion transmitting system between the turbine gate and mastercontroller through the devices designated by reference characters 26,120 and 49, in Fig. l, is connected to represent the well known selsynsystem. To avoid confusing the drawings with additional circuitconnections the complete circuit connections between devices 26 and 50and the source of supply have not been shown. Anyreliable motiontransmitting system may be used here in place of the one represented.

In some cases it may be desirable'to make the gate openingproportionalto the integrated frequency error as compared with the measured poweroutput of the alternating current generators 21 and in Fig. 16 I haverepresented the motion transmitting system, corresponding to thatdesignated by reference characters 26, 120 and 49 in Fig. 1,- as beingconnected between a wattmeter 163 measuring the output of the generator21 and the unit controller. In this case the hand 51 will representintegrated frequency error as before and hand 52- will represent poweroutput and the apparatus will be adjusted to maintain a gate openingsuch that the two hands will keep together. This arrangement isbeneficial where the measure of the fluid supplied to the prime movervaries materially.

In Fig. 16 I have also represented how the rate of the master clock may-be biased to further regulate the load distribution. Let us assume forexample that the lines 27 represent a tie line between two largedistribution systems 164 and 165 and that the controlled station isfeeding power to system 165. Consider first that the double-pole,double-throw switch 167 is thrown to the right and that switch 168 isclosed. This will connect the pendulum biasing coil 67 through arectifier 169 to current transformer 170 responsive to the current inthe tie line 27. The polarity of coil 67 is such as to produce a southpole field at its upper end opposite to the south pole of the smallpermanent magnet contained in the pendulum. Then, as the pendulum sweepspast the coil, there will be an upward force on it due to the repulsionbetween the coil and magnet. This slows down the rate of the pendulum inproportion to the current in the tie line 27. Resistance 171 is providedfor adjusting purposes. The current strength of coil 67 and the pendulumwill be so adjusted that :,when the desired amount of current isflowinghn tie line 27 the rate of the pendulum will be exactly correctto keep the frequency of the system at its normal value. Now, when aheavier current flows in the tie line, the pendulum will be slowed downvery slightly and the controlled station will of course respond to thisslower rate tending to hold the slightly lower frequency correspondingto the rate set by the pendulum until the current in the tie line isreduced to normal. On the other hand, if the current in the tie linefalls below normal, the pendulum will not be biased so much and as aresult it will oscillate slightly faster than normal until the currentin the tie line has been brought up to normal. Such changes in the rateof the pendulum are very slight of course; for example not more than afew seconds per day, but they are very effective in controlling theload.-=

A somewhat similar result is obtained if the switch 167 is thrown to theleft as shown and the switch represented at 168 is opened. Now the coil67 is energized from a constant voltage direct current source 172,having the correct polarity to produce a north pole at the upper end ofcoil 67, through a variable resistance 173 and the manually adjustableresistance 171. Resistance 173 is automatically controlled by rotationof the motion receiving motor 49 which is responsive to the gate openingor the power output measurement of generator 21 as desired. The pendulumrate is adjusted to be exactly correct with the desired load on thecontrolled unit. Now, if load on the controlled unit increases theresistance 173 is increased, thereby decreasing the current in coil 67,;the rate of the pendulum is lowered and the apparatus-which isresponsive to the pendulum tends to gradually reduce the load on thecontrolled unit or units as the case may be. This arrangement would tendto maintain a fairly constant load on the controlled units. Obviously,the manually adjustable re sistance 171 may also be used to bias thependulum for load control either with or without the automatic loadcontrol feature just described. These resistance devices 171 and 173 maybe built as a small adjustable rheostat mounted on the unit controller.

I prefer also to make provision for quickly shifting one or more of thepower generating units from complete automatic to complete manualcontrol and vice versa. One scheme for doing this is represented in Fig.17 where 135 represents the contact arm and 144 and 145 represent thehelical contacts of one of the unit controllers. 23 represents the speedcontrol motor which is controlled'by the contacts 135, 144 and 145during automatic operation. Contact arm 135 is represented as energizedfrom line 102 through a relay operated switch 175. When the manuallyoperated switch 176 is closed, coil 177 of the relay is energizedclosing switch 175 for automatic opcator 44, Fig. 1, is useful in theone or the other of a pair of contacts oration. When the switch tact 178establishes is closeda back cona holding circuit for the coil Switch 179is provided for manual control. As shown, it is in a neutral position,but when turned in either direction contact arm 180 short circuits coil177, permitting switches 178 and 175 to open. The other contact arm 181energizes which are connected in parallel with contacts 144 and 145.Consequently, 23 is shifted from automatic to manual control. As soon asthe switch is brought back to the neutral position shown, switches 175and 178 close again, bringing the control of motor 23 back to theautomatic device. If permanent manual control is desired, switch 176isopened. This arrangement does not otherwise interfere with theoperation of the unit controller and, as pointed out previously, theunit controller is so built as not to become damaged by an abnormaldisplace-- ment of the two hands 51 and 52 such as might occur duringmanual control. The station indiinitial adjustment of the unitcontrollers and facilitates manual control operations by itsindications.

The apparatus previously described is more or less complicated and Ihave found that these complications are justified where a large amountof power feeding an extensive distribution system is involved. When theinvention is to-be used on small isolated generating plants theequipment may be simplified considerably, and in Figs. 18, 19 and 20 Ihave represented such simplified embodiments of the invention.

In Fig. 18, 190 represents an inverted rotary supplied from a directcurrent source 191 and supplying an alternating current system 192. At42A I have represented a motion reproducing motor similar to motor 42 inFig. 1. controlled by the automatic master clock regulator, not shown,as previously explained. The unit controller 47 of Fig. 1 is replaced bya rheostat 193 operated by motor 42A. This rheostat controls a the phaserelation of the-master clock cam 71,

Fig. 1, shall be corrected by a very rapid correction of the frequency,rather than by the means previously described.

In Fig. 20 I have represented a direct mechanical connection between themaster clock and 'the rheostat 193. In this case the upper end of theauxiliary pendulum 73 serves as a driving pawl for ratchet wheels 196and 197, suitably geared or otherwise mechanically connected to therheostat 193 for regulating the frequency and to the wheel 94A forcorrecting the position of cam 71 which is driven by the synchronousmotor 32 in accordance with the frequency of system 192. It will beunderstood that the accumulated error in frequency as measured by themaster clock over a two-second interval will determine the position ofthe, auxiliary pendulum 73 when it is moved upward, such that the di-'by this switch the control of motor 9 ulation, are nevertheless intendedto be includ within the scope of nrv invention.

In the foregoing I have described apparatus for controlling thefrequency of a power station having. one or more prime mover'drivengenerating units. If the stationthus controlled is one of the main powerstations of alarge distribution system and is capable of taking care ofa large portion of the variation in load on the system it may sufiice tocontrol the frequency of the entire'system economically. However it maybe desirable to provide similar control apparatus at two or more of theimportant power stations of a large distribution system, which stationsmay be located hundreds of miles apart.

I have found that the master clock pendulum may be made with such a highdegree of time accuracy that the use of two such pendulumssimultaneously operating control apparatus at different stations feedingthe same distribution system is entirely feasible.

In accordance with the provisions of the patent statutes I havedescribed the principle of operation of my invention, together with theapparatus which I now consider to represent the best embodiment thereof,but I desire to have it understood that the apparatus shown anddescribed is only illustrative and that the inven-- tion may be carriedout by other means.

What I claim as new and desire to secure by Letters Patent of the UnitedStates, is:

1.fControl apparatus for alternating current systems distributing powerand time comprising in combination with a power station containingregulatable power generating apparatus for supplying alternating currentto the system, apparatus including a master clock for measuring theintegrated frequency errors of the system occurring over successiveshort time intervals not exceeding a few seconds in duration, electriccontacts controlled by said master clock in response to such errormeasurements, if any, an electrical signal transmitting systemcontrolled by said contacts for electrically distributing suchmeasurements, and means connected to said system comprising a device fortotalizing the transmitted measurements and giving an indication of thetotalled integrated frequency error of the system as well as themagnitude and direction of each individual frequency error measurementto facilitate the control of said power station.

2. In a regulating system for alternating current power systemsdistributing power and time, apparatus for measuring integratedfrequency errors of the power system occurring over consecutive timeintervals not exceeding a few seconds in duration, electric contactscontrolled by said measuring means in response to the magnitude anddirection of the consecutive error measurements, if any, an electricmotion transmitting system controlled by said contacts, saidtransintervals not exceeding a few seconds duration,

and means responsive to each such measurement for regulating the speedof the alternating current generator so as to maintain the totalintegrated frequency error of the system proportional to the load onsaid alternating current generator but within such limits that thesystem frequency may be used as a standard of time without objectionableerror.

4. A system for distributing power and time by alternating current ofregulated frequency, comprising alternating current generatingapparatus, a system of distribution supplied thereby, a pendulum typemaster clock, means having a rate of movement dependent upon thefrequency of the system such that when the frequency is correct saidmeans has a cycle of movement which is

